ICAO Airspace Classification (A–G)

ICAO Airspace Classification (A–G)

Which service you receive, whether you are separated from other traffic, and whether you must be on the radio all depend on one thing: the class of airspace you are flying in. ICAO Annex 11 defines seven classes, A to G, graded by the level of air traffic control service; in the EU the details are laid down in SERA.6001 and Appendix 4 of Regulation (EU) No 923/2012. Airspace classes are among the most heavily tested topics in Air Law — learn the table until it is second nature.

Controlled vs uncontrolled

• Classes A, B, C, D and E are controlled airspace — an ATC service is provided.
• Classes F and G are uncontrolled airspace.
• Class A is the only class in which VFR flight is not permitted.

Class overview (VFR perspective)

Memory hook: radio and clearance are mandatory for VFR in B, C and D; not required in E, F and G. VFR flights are therefore not required to continuously monitor a radio frequency in airspace G and E — but they always are in B, C and D.

VMC minima (SERA.5001) — the visibility and cloud rules

• At and above FL100: flight visibility 8 km; distance from cloud 1500 m horizontally, 1000 ft (300 m) vertically.
• Below FL100 (above 3000 ft AMSL / 1000 ft AGL): flight visibility 5 km; same cloud distances. Example: for a VFR flight at 5000 ft in Class B, the minimum flight visibility is 5 km, with 1500 m horizontal and 300 m vertical distance from cloud.
• In classes F and G at or below 3000 ft AMSL or 1000 ft AGL (whichever is higher), the base rule is: flight visibility 5 km, clear of cloud and with the surface in sight. A reduction to 1500 m flight visibility is permitted when flying at 140 kt IAS or less (allowing adequate time to see and avoid); 800 m applies only to helicopters manoeuvring at a speed that allows other traffic and obstacles to be seen in time.
• Speed limit: maximum 250 kt IAS below FL100 (except where otherwise authorised).

Class C in detail

Class C is where VFR pilots meet "real" ATC:

• In airspace C, VFR flights are separated from IFR flights and receive traffic information about other VFR flights (avoidance advice on request).
• Continuous radio monitoring on the frequency of the appropriate ATC unit is obligatory, and an ATC clearance is required to enter.
• VMC minima as above: 8 km at and above FL100, 5 km below; cloud distance 1500 m / 1000 ft.

Abnormal situations in Class C:

• Radio failure before entry: if radio contact is lost after receiving the entry clearance but before entering Class C, the airspace must be avoided despite the clearance.
• Radio failure inside Class C below FL100 near international aerodromes: continue according to the last acknowledged ATC clearance if possible; otherwise leave the airspace by the shortest route while remaining in VMC.
• Unable to maintain VMC: inform ATC immediately and request an amended clearance (climb, descent or heading change) that lets you regain visual conditions.
• Transponder failure: inform the appropriate ATC unit immediately.

Class D

In Class D, VFR flights are not separated from anyone. They receive traffic information about IFR flights (avoidance advice on request) and about other VFR flights. Radio and clearance are mandatory. Collision avoidance remains fully with the pilot — traffic information tells you where to look, not that you are safe.

Class E

• VFR traffic is not separated from any other traffic; VFR flights can expect traffic information as far as practicable.
• Radio contact and clearance are not required for VFR.
• VMC minima below FL100: 5 km visibility, cloud distance 1500 m horizontally / 1000 ft vertically.

Classes F and G — uncontrolled

• Class F provides an advisory service to participating IFR flights only; VFR flights receive FIS. Class F is rarely used in Europe.
• Class G has no separation at all; FIS is available on request. Reduced low-level VMC minima apply as described above (base rule 5 km, clear of cloud, surface in sight).

Formation flight (SERA.3135)

Aircraft may only be flown in formation after previous agreement among the pilots-in-command; in controlled airspace, additional conditions prescribed by the competent authority and ATC apply. Formation flight is not limited to uncontrolled airspace.

Restricted areas

Restricted areas are airspace in which flight is subject to restrictions — crossing is possible only under the published conditions (see NOTAM/AIP).

Germany (national)

Germany applies the ICAO/SERA classes as follows:

• Class A is not used.
• Control zones (CTR) are classified as Class D.
• Class C extends from FL100 (FL130 in the Alpine area) up to FL660.
• Class E generally begins at 2500 ft AGL; in designated areas it is lowered to 1700 ft or 1000 ft AGL. It extends up to FL100 (the base of Class C).
• Class G lies below Class E down to the surface.
• Additionally, Germany uses RMZ, TMZ and D(CTR) in accordance with SERA/ICAO.

Transponder rule: powered aircraft on VFR flights must operate the transponder (Mode A+C or Mode S) on their own initiative above 5000 ft AMSL or above 3500 ft AGL, whichever is higher — in practice this concerns Class E cruising flight. Code 7000 is the VFR standard code.

TMZ (Transponder Mandatory Zone): before entering, the transponder must be switched on with Mode A+C or Mode S active.

RMZ (Radio Mandatory Zone): an RMZ is Class G airspace with mandatory radio — an initial call before entry, then continuous monitoring of the frequency until leaving the zone. Practical point: when you hear an IFR flight approaching the runway in an RMZ, scan visually in the direction of its approach — IFR traffic does not automatically give way to VFR.

ATZ (Aerodrome Traffic Zone): the airspace element surrounding an (uncontrolled) aerodrome established to protect aerodrome traffic.

Exam essentials

• Classes A–E are controlled, F and G uncontrolled; VFR is not permitted in Class A.
• Radio and clearance are mandatory for VFR in B, C and D; not required in E, F and G — so continuous listening watch is not required in G and E.
• Class C: VFR is separated from IFR and receives traffic information about other VFR (avoidance advice on request).
• Class D: VFR is not separated; it receives traffic information about IFR and VFR flights.
• Class F advisory service applies to participating IFR flights only; VFR receives FIS.
• Low-level VMC in F/G: 5 km, clear of cloud, surface in sight; 1500 m allowed at 140 kt IAS or less; 800 m only for helicopters.
• Formation flight requires prior agreement of the pilots; in controlled airspace additional ATC/authority conditions apply.
• Germany: no Class A; CTR = Class D; Class C from FL100 (FL130 Alps) to FL660; Class E from 2500 ft AGL (1700/1000 ft in designated areas) up to FL100.
• An RMZ is Class G with mandatory radio; a TMZ requires Mode A+C or Mode S before entry.